EP1387503A1 - A method for allocating a direction of transmission of time slots in a frame of a transmission system with time separation of the transmission in uplink and downlink, and a corresponding transmission system - Google Patents

Abstract

The method allows time slots (ts1,ts2,ts3,ts4) of the time frames (fr1) for a radio system, e.g. a cellular mobile radio system, to be assigned upload (UL) and download (DL) transmission directions, so that each pair of adjacent time frames have the same number of time slots assigned to upload and download transmission directions. The transmission direction is altered for at least one time slot in the second time frame relative to the same time frame in the first time slot. Also included are Independent claims for the following : (a) a radio system with time offset between upload and download transmissions; (b) a radio network controller; (c) a core network of a radio system.

Description

The invention relates to a method for assigning a Direction of transmission for time slots of time frames one Radio systems with temporal separation of transmission in uplink and downward direction. The invention further relates to a Radio system with temporal separation of transmission in uplink and downward direction with at least one device to assign a transmission direction for time slots from Time frame, as well as a corresponding five-access controller and a corresponding core network.

In radio systems, both signaling data and organizational information (for example control signals or information about the quality of the connection) as well as user data (e.g. language, image information or others Data) by means of electromagnetic waves via a radio interface between sending and receiving station transfer. A separation of the transmission in the upward direction (Uplink - UL), i.e. from a subscriber station to a base station, from the transmission in the downward direction (downlink - DL), i.e. from the base station to a subscriber station, can either by choosing different time slots, i.e. via Time Division Duplex (TDD), or by choosing different ones Frequency bands, i.e. Frequency Division Duplex (FDD) respectively.

A radio system with temporal separation of the transmission in Upward and downward direction (TDD radio system) like UTRA-TDD (Universal Terrestrial Radio Access - Time Division Duplex) or TD-SCDMA (Time Division - Synchronous Code Division Multiple Access) is particularly well suited to an asymmetrical Allow transmission.

In Figure 1, the temporal structure of the transmission in one Radio system with temporal separation of the transmission in Upward and downward direction shown schematically. Within a time frame for fr, fr 'becomes individual time slots ts1, ts2, ts3, ts4, ts5, ts6, ts7, ts8 each a transmission assigned in upward UL or downward direction DL. ever according to data transmission requirements, the number of Time slots ts1, ..., ts8 in the upward direction UL or downward direction DL set so that, for example, for viewing a larger number of time slots of a video ts1, ..., ts8 in the downward direction DL than in the upward direction UL operated. The allocation of the time slots ts1 ..., ts8 in the upward UL or downward direction DL can thereby change from one to the next timeframe fr, fr '. Two in a row Timeframe fr, fr 'with different asymmetry between upward UL and downward direction DL are in Figure 1 shown. The ratio of upward UL to downward direction DL is 1: 1 in the first time frame for fr and 1: 3 in second time frame for '.

The data transmission in radio cells of a radio system is disturbed by interference with neighboring radio cells. In a radio system with a separation of upward and downward direction in frequency bands (FDD radio system) it can be used same time both to interference of a base station a radio cell with subscriber stations of neighboring radio cells as well as interference from a subscriber station Radio cell come with the base stations of neighboring radio cells. The aforementioned interference occurs in an FDD radio system on when in neighboring radio cells at the same time is sent or received. These interferences result also in radio systems with temporal separation of the transmission in upward and downward direction (TDD radio systems), if in neighboring radio cells in the same time slots same transmission direction is used. In a radio system with temporal separation of the transmission in upwards and Downward direction also creates additional interference on. The additional interference from radio systems with temporal separation of the transmission in upward and downward direction arise when in neighboring radio cells different transmission directions in the same time slot Upward and downward direction can be used. Arise then interference of the subscriber stations of neighboring radio cells with each other as well as interference of the base stations neighboring radio cells with each other.

To minimize the interference for all connections to design, procedures for dynamic channel assignment (Dynamic Channel Assignment - DCA) applied. For dynamic Channel assignment, measurements of the transmission channels are carried out. The evaluation of the measurements and the channel assignment is ideally on a higher layer (layer) such as the Radio Network Controller (RNC) in the UTRAN (Universal Terrestrial Radio Access Network). There there is not only information about interference in one single radio cell but via interference of several radio cells in front. Through the channel assignment in a higher layer however, there are also delays due to signal transmission as well as an overload of signaling data, so that changes in interference - caused e.g. due to the mobility of the subscriber stations - only with reduced Flexibility can be responded to.

A method is known from DE 198 08 948 C2, the individual Connections assigns changing time slots. By doing radio communication system described in said patent organizational information is stored in a fixed time slot transmitted by radio cells. So that all participants have an opportunity have the organizational information of neighboring radio cells eavesdropping, it must be ensured that a participant not exclusively in that assigned to your own radio cell Receives time slot with organizational information. To serves the process of the patent, which is always different Participants in the time slot with organizational information can be received so that all participants have the opportunity the organizational information of the neighboring radio cells receive.

The invention is therefore based on the object of a method specify with which the in a radio system with temporal Separation of the transmission in the upward and downward direction Interferences occurring favorably influenced can be.

This task is accomplished with the method with the features Claim 1 and the radio system with the features according to claim 9 solved.

Advantageous developments and further developments of the invention are the subject of the dependent claims.

In the method according to the invention for assigning a transmission direction for time slots of time frames of a radio system with temporal separation of the transmission in upwards and Downward direction, time slots will be in a first time frame each assigned a direction of transmission. The time slots will be in a second timeframe that is timed directly the first time frame is followed by one each Direction of transmission assigned. The number of Upward time slots and the number of time slots down in the first time frame the respective number in the second time frame. For at least the transmission direction becomes one time slot per transmission direction in the second time frame compared to the first Timeframe changed.

By changing the direction of transmission as described above become the interference conditions caused by the change the time slots affected in the direction of transmission changed. In neighboring radio systems with time separation of the transmission in the up and down direction as well as within one Radio system with temporal separation of the transmission in Up and down direction can thus from interference from Base stations with each other and interference from subscriber stations with each other, for example interference from base stations with subscriber stations or vice versa. The Changing the transmission direction can therefore lead to more favorable interference conditions for those of changing the direction of transmission affected time slots.

In the following, mobile stations are exemplified as subscriber stations considered without the invention being limited thereto should be.

It is particularly advantageous if an assignment of the Direction of transmission of the time slots according to an assignment rule he follows. The assignment rule can be sent to special Conditions of the radio system with time separation adapted to the transmission in the upward and downward direction and so for the largest possible number of time slots of a time frame cause better interference conditions. The assignment rule can be such that Time slots with very high interference with time slots can be interchanged with very little interference.

Within a radio system with temporal separation of the transmission in the up and down direction, that over several Radio cells, it is useful if at least two adjacent radio cells have different assignment rules be used. This way you can ensure be that in the radio cells a change in the direction of transmission to be changed for the affected time slots Interference conditions leads. Within the radio system with temporal separation of the transmission in upward and downward direction interferences become better across all time slots distributed or averaged.

If several assignment rules are available, then according to a further embodiment of the invention, the assignment rule randomly determined. This is done a change in the interference conditions with less need for signaling, because a selection process for the best Allocation rule is not required.

The transmission direction is advantageously assigned of the time slots for further time frames repeated. The repetition in time makes it possible from that previously mentioned advantage of improving the interference conditions for as many of the time slots in a time frame as possible or to be able to benefit repeatedly, so that in the Radio system with temporal separation of transmission in uplink and downward the interference across all time slots distributed or averaged.

In particular, it is beneficial if the assignment of the transmission direction the time slots for at least one, the second time frame immediately following, third time frame, with the assignment of the transmission direction of the time slots of the second time frame.

In the radio system with temporal separation of the transmission in Up and down direction, conditions, which lead to interference, i.e. the number of mobile stations in a radio cell and the allocation of the time slots constantly changing through the mobile stations. It is therefore convenient if instead of a fixed allocation rule a time changing allocation rule is used, the flexibly adapted to the current interference conditions can be.

If the assignment rule proves the direction of transfer a random principle, there is an advantage from that all interference between mobile stations and between Average base stations automatically over time. On this way can be in any radio system with time Separation of the transmission in the upward and downward direction all temporal changes in the interference conditions take into account and averaging the interferences, without special assignment rules or even dynamic Mechanisms for channel assignment would be necessary. in the In individual cases, even less interference can be achieved on average than would be the case if only the one Interference mechanisms occurring FDD radio system occur would.

The radio system with temporal separation of the transmission in Up and down direction, the radio access controller and the core network are responsible for carrying out the procedure necessary components.

Fig. 1:

ein Schema einer bekannten Struktur von zwei Zeitrahmen mit Zeitschlitzen eines Funksystems mit zeitlicher Trennung der Übertragung in Aufwärts- und Abwärtsrichtung,

Fig. 2 mit Teilfigur 2a:

ein Schema eines Ausschnitt eines erfindungsgemäßen zellularen Mobilfunksystems zu einem Zeitpunkt t₀, und

Teilfigur 2b:

ein Schema eines Ausschnitts des erfindungsgemäßen zellularen Mobilfunksystems nach Figur 2 zu einem Zeitpunkt t₀+ Δt,

Fig. 3:

ein Schema eines zeitlichen Ablaufs einer Zuweisung der Übertragungsrichtung für Zeitrahmen einer Funkzelle mit einer Mobilstation,

Fig. 4:

Schema eines erfindungsgemäßen Mobilfunksystems nach dem UMTS-Standard (UMTS: Universal Mobile Telecommunications System).

The invention and details are explained in more detail below with reference to exemplary embodiments shown in the figures. Show it:

Fig. 1:

1 shows a schematic of a known structure of two time frames with time slots of a radio system with temporal separation of the transmission in the upward and downward direction,

2 with partial figure 2a:

a schematic of a section of a cellular mobile radio system according to the invention at a time t ₀ , and

Sub-figure 2b:

2 shows a schematic of a section of the cellular mobile radio system according to the invention according to FIG. 2 at a time t ₀ + Δt,

Fig. 3:

1 shows a diagram of a time sequence of an assignment of the transmission direction for time frames of a radio cell with a mobile station,

Fig. 4:

Scheme of a mobile radio system according to the invention according to the UMTS standard (UMTS: Universal Mobile Telecommunications System).

This was already shown in FIG. 1 in the introduction to the description shown scheme of a frame structure with time slots a radio system with temporal separation of the transmission in Described upward and downward direction.

For the sake of clarity, FIGS Radio system with temporal separation of transmission in uplink and downward direction, hereinafter briefly TDD radio system called, with four time slots per time frame and one Participants per radio cell described. The time frames of the radio cells are synchronized in time. The designs are available analogously, however, for all radio systems that transmit in TDD mode, especially for UTRA-TDD and TD-SCDMA. Of course the method can also be used if in each radio cell there are several users available standing time slots are distributed and if the time frame are not synchronized.

Also in other radio systems such as ad hoc networks (also self-organizing Called networks), the invention is straightforward applicable and can lead to the advantages described above.

Figure 2 is composed of the sub-figures 2a (top) and 2b (below), with largely identical in both sub-figures Reference numerals are used.

In the scheme according to the invention shown in partial figure 2a of a TDD radio system is divided into seven radio cells z1 z2, z3, z4, z5, z6, z7 transmitted in time frames fr1, each four Time slots ts1, ts2, ts3, ts4 included. The time slots ts1, ts2, ts3, ts4 is an upward transmission direction UL or downlink DL assigned. Every radio cell z1 ..., z7 each have a base station and a mobile station, the invention can also be applied if radio cells z1, ..., z7 do not have their own base station and / or several mobile stations in a radio cell z1, ..., transfer z7.

Different asymmetries exist in the individual radio cells z1 ..., z7 at time t ₀ , ie different numbers of time slots ts1, ts2, ts3, ts4 are used in the upward UL or downward direction DL. In radio cell z1, for example, three time slots ts1, ts2, ts3 in the upward direction UL and one time slot ts4 in the downward direction DL are used, while the opposite is the case in radio cell z3. For the radio cells z1 and z3 there is therefore interference between the respective base stations and between the respective mobile stations for the time slots ts2 and ts3. In the time slots ts1 and ts4, on the other hand, only interference of the base stations with the mobile stations occurs.

In part figure 2b in the diagram from part figure 2a the occupancy of the time slots ts1, ts2, ts3, ts4 at a later point in time t ₀ + Δt is shown in a time frame fr2 which follows the first time frame fr1 directly in time. The exact value of Δt is given for each radio system in accordance with the specifications applicable there. The example of radio cells z1 and z3 shows that with the same asymmetry as at time t ₀ , i.e. unchanged number of time slots in the upward direction UL and unchanged number of time slots in the downward direction DL, interference now occurs in the time slots ts1 and ts4 between the respective base stations and occur between the respective mobile stations. For the time slots ts2 and ts3, only interference of the base stations with the mobile stations now occurs. Similar results can be found when considering the other radio cells z2, z4, z5, z6, z7 in comparison with their respective neighboring radio cells. At further subsequent times, the transmission directions for the time slots ts1, ts2, ts34, ts4 of a radio cell z1, ..., z7 are changed again compared to a previous time. As a result of this constant change in the transmission direction assigned to a time slot ts1, ts2, ts3, ts4 of a radio cell z1 ..., z7, different interference conditions occur at different times, so that the interference in the time slots ts1, ts2, ts3, ts4 is averaged over time a radio cell z1 ..., z7. By changing the type of interference in a time slot ts1, ts2, ts3, ts4, this can even lead to lower interferences being achieved than would be the case in an FDD radio system.

An assignment of the transmission direction of the individual time slots ts1, ts2, ts3, ts4 for each radio cell after one Allocation rule regulated by a list of Allocation rules are determined randomly. The respective ZV allocation rule, i.e. the one for one immediately following Time frame fr1, fr2 intended allocation, becomes mobile stations the radio cells z1 ..., z7 via a not shown Organizational channel communicated a time slot ts1, ts2, ts3, ts4 of a time frame fr1, fr2 occupied and thereby already one for this time slot ts1, ts2, ts3, ts4 Direction of transmission downward direction DL. The allocation rule ZV thus extends to all remaining ones Time slots ts1, ts2, ts3, ts4 of a time frame fr1, fr2.

Interference over the individual is particularly good Distribute time slots ts1, ts2, ts3, ts4 on average, in which not only repeated reassignment of Upward UL and downward direction DL to the individual time slots ts1, ts2, ts3, ts4 but also the assignment rule ZV is changed again and again. In particular, if the allocation of a time slot ts1, ts2, ts3, ts4 to Upward UL or downward direction DL is purely random, the interference is well averaged for everyone Time slots ts1, ts2, ts3, ts4 of all radio cells. A targeted one The choice of a ZV allocation rule can also be omitted such as the use of elaborate dynamic processes Channel assignment.

. Diese möglichenFIG. 3 shows a diagram of the change in the transmission direction of the time slots ts1, ts2, ts3, ts4 in time frames fr1, fr2, fr3, fr4, fr5, fr6 of a radio cell z1, ..., z7. All time slots ts1, ts2, ts3, ts4 are occupied by a single subscriber and the asymmetry is fixed. At times t ₀ to t ₀ + 5Δt all possible arrangements of the time slots ts1, ts2, ts3, ts4 are shown. If k is the number of all time slots and n is the number of time slots in the upward UL or downward direction DL, the number of all possible arrangements is given by the mathematical expression

, These possible

Arrays are chosen randomly so as to be a good averaging of interference. The second and third Time frames fr2, fr3 and the fourth and fifth time frames fr4, fr5 have the same assignments for the time slots ts1, ts2, ts3, ts4 for upward UL and downward direction DL. In further, not shown embodiments of the invention however, it is also possible to assign the time slots ts1, ts2, ts3, ts4 either for any number of time frames to leave fr1, ..., fr6 unchanged or even in any time frame to change fr1, ..., fr6.

In a further embodiment of the invention, not shown, the time slots ts1, ts2, ts3, ts4 are occupied by different subscribers and / or several different subscribers are assigned to at least one of the time slots ts1, ts2, ts3, ts4 simultaneously (for example by means of code division multiple access) CDMA). In this case, the interference conditions for the participants can also change in that the time also for time slots ts1, ts2, ts3, ts4 of a time frame fr1 ..., fr6 with the same transmission direction upward UL or downward direction DL (but possibly different participants) Position is changed in the following time frames fr1, ..., fr6. Based on the first time frame fr1 of FIG. 3, this embodiment of the invention would correspond, for example, to an exchange of the third time slot ts3 with the fourth time slot ts4 while at the same time maintaining the occupancy of the first two time slots ts1, ts2. Since all time slots ts1, ts2, ts3, ts4 are distinguishable and can be arranged, there are, with k the number of time slots, k ² possibilities with fixed asymmetry to assign the time slots to upward UL and downward direction DL.

No detailed explanation requires that even one of asymmetry changing from one time frame to the next time frame does not affect the operation and success of the process.

In Figure 4 is a diagram of a mobile radio system according to the invention shown according to the UMTS standard. A core network CN is via interfaces Iu with the UTRAN (Universal Terrestrial Radio Access Network) connected. The UTRAN exists from several RNS (Radio Network Subsystem) subsystems that each have a data line Iu to the core network CN. affiliated There is always a radio network controller at each interface Iu RNC (Radio Network Controller), which in turn via Interfaces Iub connected to several base stations Node B. is. Each base station Node B can (e.g. via sector antennas) several radio cells are assigned to the radio system his. The interface between UTRAN and a subscriber device UE (User Equipment), for example a mobile station, takes place via the air interface Uu by means of a radio link. The radio network controller RNC of various subsystems RNS are usually referred to each other via an Iur Interface connected. In the RNC radio network controllers and / or there are facilities E in the core network CN, the directions of transmission of the time slots of a time frame Assign upward UL and downward direction DL.

Also the assignment rule ZV for the direction of transmission can be stored in the device E or determined become. The assignment rule is transmitted by the core network CN to a radio network controller RNC in an organizational channel via an interface Iu. From the radio network control 1er RNC is also the assignment rule ZV in one Organizational channel via the Iub interfaces to the base stations Transfer Node B and from there via an organizational channel the air interface Uu the user equipment UE communicated.

Claims (11)

Method for assigning a transmission direction for time slots (ts1, ts2, ts3, ts4) from time frames (fr1, fr2) of a radio system with temporal separation of the transmission in upward (UL) and downward direction (DL), in which Time slots (ts1, ts2, ts3, ts4) are each assigned a transmission direction (UL, DL) in a first time frame (fr1), a transmission direction (UL, DL) is assigned to the time slots (ts1, ts2, ts3, ts4) in a second time frame (fr2), which follows the time directly after the first time frame (fr1), the number of time slots (ts1, ts2, ts3, ts4) in the upward direction (UL) and the number of time slots (ts1, ts2, ts3, ts4) in the downward direction (DL) in the first time frame (fr1) equal to the respective number in the second Time frame (fr2) is the transmission direction in the second time frame (fr2) is changed for at least one time slot (ts1, ts2, ts3, ts4) per transmission direction compared to the first time frame (fr1). The method of claim 1, wherein an assignment of the direction of transmission of the time slots (ts1, ts2, ts3, ts4) according to an assignment rule (ZV) takes place. The method of claim 2, wherein the radio system has several radio cells (z1, ..., z7) and in at least two neighboring radio cells (z1, ..., z7) different assignment rules (ZV) are used. The method of claim 2 or 3, wherein the assignment rule (ZV) is determined randomly. Method according to one of claims 2 to 4, in which the assignment of the direction of transmission of the time slots (ts1, ts2, ts3, ts4) for further time frames (fr2, ..., fr6) repeated in time. The method of claim 5, wherein the assignment of the direction of transmission of the time slots (ts1, ts2, ts3, ts4) for at least one, the second Timeframe (fr2, fr4), immediately following, third Time frame (fr3, fr5), with the assignment of the transmission direction the time slots (ts1, ts2, ts3, ts4) of the second time frame matches. Method according to one of claims 2 to 6, in which the allocation rule (ZV) changes over time. Method according to one of claims 2 to 7, in which the assignment rule (ZV) the direction of transfer the time slots (ts1, ts2, ts3, ts4) at random assigns. Radio system with temporal separation of the transmission in upward (UL) and downward direction (DL), with at least one device (E) for assigning a transmission direction for time slots (ts1, ts2, ts3, ts4) of time frames (fr1 ..., fr6), in which the device (E) time slots (ts1, ts2, ts3, ts4) in a first and in a second time frame (fr1, fr2), which follows the first time frame (fr1), each assigns a transmission direction, the number of time slots (ts1, ts2, ts3, ts4) in the upward direction (UL) and the number of time slots (ts1, ts2, ts3, ts4) in the downward direction (DL) in the first time frame (fr1) equal to the respective number in the second time frame ( fr2) is in which the device (E) changes the transmission direction in the second time frame (fr2) for at least one time slot (ts1, ts2, ts3, ts4) per transmission direction compared to the first time frame (fr1). Radio network controller (RNC) of a radio system according to claim 9, comprising a device (E) for assigning a Direction of transmission for time slots (ts1, ts2, ts3, ts4) of time frames (fr1, ..., fr6). Core network (CN) of a radio system according to claim 9 or 10, with a device (E) for assigning a transmission direction for time slots (ts1, ts2, ts3, ts4) of time frames (fr1, ..., fr6).

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